This invention relates to a pipe cutter and more particularly to a portable power saw for cutting pipe and rods.
Copper tubing, plastic pipe and electric conduits are generally cut by a hand saw or by a pipe cutter tool with two guide rollers and a cutting disk that is advanced toward the pipe and the two rollers and is rotated about the axis of the pipe to sever the pipe. Both of these pipe cutting procedures are slow and require substantial physical effort.
The handsaw that is commonly used is a hacksaw. Hacksaws have a thin steel blade held in a frame and subjected to a tension load. These saws are difficult to guide accurately to form a straight cut. Cuts that are perpendicular to a pipe center line are desirable when attaching a pipe to a coupling. If the coupling is threaded, the end of the pipe that is inserted into the coupling must also be threaded. To cut good threads on a pipe, the end of the pipe must be perpendicular to the pipe center line. If the end is not perpendicular the threads may be crooked. A coupling that is connected by solder or adhesives usually includes a flange or stop members that limit penetration of the pipe into the coupling. If the end of the pipe is not perpendicular to the axis of the pipe, the pipe will not seat properly in the coupling.
Hack saw blades have small closely spaced teeth to cut material. These blades remove small particles of material on each cutting stroke and are therefore slow. It can take several minutes to cut one pipe. Even an exceptionally strong person can only cut a limited number of pipes per day due to the force and time required to make each cut.
The pipe cutters that have two rollers and a cutting disk generally work well and require minimal force from the operator. If the axis of the cutting disk is not parallel to the axis of the two rollers, the cutting disk will tend to form a spiral groove and move along the axis of the pipe. A more serious problem that occurs, even when the cutting disk is working properly, is a reduction in the inside diameter of the pipe where the pipe is cut. This reduction in the inside diameter of a cut fluid conveying pipe reduces flow rate and increases the pressure drop along the length of the system when fluid is flowing. The reduced inside diameter in electrical conduit increases the difficulty of pulling wire through the pipe. The ends of the pipe sections with reduced internal diameter have a sharp edge which can damage or even destroy the insulation covering on electrical wiring. The sharp edge can be eliminated with a reamer but the reduced diameter cannot be easily restored to the original diameter. This makes it more difficult to pull electrical wires through the pipe and reduces the number or the size of the wires that can be received in the pipe.
An object of the invention is to provide a power saw for cutting pipe.
Another object of the invention is to provide a power saw with a guide for restraining a pipe while it is cut.
A further object of the invention is to provide an attachment for a jigsaw that guides a jigsaw blade while cutting a pipe.
The pipe cutter includes a motor driven jigsaw with a saw blade that is reciprocated back and forth. A way member is clamped to the jigsaw by fasteners. A workpiece holder with a workpiece slot is slidably mounted on the way. Stops limit movement of the workpiece holder relative to the way.
The workpiece holder can be provided with multiple workpiece slots to accommodate pipes with different diameters. A handle is attached to the workpiece holder for moving the workpiece holder relative to the way. The handle has a pipe contact surface which cooperates with the workpiece slot to hold a pipe perpendicular to the path of movement of the workpiece holder.
The workpiece holder is slideably mounted on the way. A workpiece slot is provided in the workpiece holder for a pipe of the diameter of that which is to be cut. A pipe that is to be cut is inserted into the workpiece slot. The workpiece holder is then advanced toward the saw blade. The force exerted to hold the saw blade in contact with the pipe being cut urges the pipe into contact with the bottom or base of the workpiece slot.